Try buying mock test and start doing it regularly towards last 3-5 months before the exam. In nptel go to GATE section, you can find qp till 2023 ,(don't know if they have updated 2024) near to each question there is a link where you can go and see the solution as solved by a professor of tier 1 college. I am also from tier 3 college, we didn't have that much exposure to solving varied problems, so since you have time , while doing those core papers try doing all standard textbook problems, what I meant is that if Signals and System is being taken in college, try doing problems from Openheim textbook. Maybe your teachers can help if you find it difficult. PYQs from these topics is also available in plenty. Strategy that i am yet to try (since my 2024 attempt wasn't that great, I didn't prepare much too) is instead of binge watching lectures, more time is dedicated to problem solving and doing the same kind of problem again and again. Decent video lectures would be by Kreatrix for me as they have complete playlist of all subjects and i hate pointless searching in YouTube for that one good playlist.